Hi I have a daughter my daughter sweats when breastfeeding or sleeping too the main area that has a lot of sweat is behind the head of my daughter?

Likely abnormal. Please discuss with her pediatrician. It is likely abnormal finding. But never get worried from an internet answer before discussing specifics with a doctor.
Does not seem. This does not seem concerning. If she is not having difficulty feeding and is not constantly crying as if something is wrong, then sweating doesn't seem to be too much of an issue. Just monitor her and keep her in a cool place such as in a fan or a/c making sure she is not hot or dehydrated. Also monitor to make sure her color doesn't change while feeding as this could mean more underlying issues.
Does she have a ... Fever? Is she eating well, gaining weight? Has she always sweated like this? If the answers (in order) are no, yes, yes and yes, there is nothing to worry about. It is probably normal for her. However, if the environment is hot, or she is overdressed or covered with too many blankets, etc, that may be making her sweat too.